1. Field
The present application relates generally to wireless communications, and more specifically to techniques for synchronizing a femto cell to a macro cell in a wireless communication network.
2. Background
Wireless communication networks are widely deployed to provide various communication content such as voice, video, packet data, messaging, broadcast, etc. These wireless networks may be multiple-access networks capable of supporting multiple users by sharing the available network resources. Examples of such multiple-access networks include Code Division Multiple Access (CDMA) networks, Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA) networks, and Single-Carrier FDMA (SC-FDMA) networks.
In recent years, users have started to replace fixed line broadband communications with mobile broadband communications and have increasingly demanded great voice quality, reliable service, and low prices, especially at their home or office locations. In order to provide indoor services, network operators may deploy different solutions. For networks with moderate traffic, operators may rely on macro cellular base stations to transmit the signal into buildings. However, in areas where building penetration loss is high, it may be difficult to maintain acceptable signal quality, and thus other solutions are desired. New solutions are frequently desired to make the best of the limited radio resources such as space and spectrum. Some of these solutions include intelligent repeaters, remote radio heads, pico cells, and femto cells.
The Femto Forum, a non-profit membership organization focused on standardization and promotion of femto cell solutions, defines femto access points (FAPs), also referred to as femto cell units, to be low-powered wireless access points that operate in licensed spectrum and are controlled by the network operator, can be connected with existing handsets, and use a residential digital subscriber line (DSL) or cable connection for backhaul. In various standards or contexts, a FAP may be referred to as a home node B (HNB), home e-node B (HeNB), access point base station, etc.
In order to keep the expenses low, it is desired for FAPs to require very little for installation and setup. This means that a FAP may be designed to auto-configure itself such that the user only needs to plug in the cables for the internet connection and electricity, and the timing and frequency synchronization of the FAP with the macro cell is taken care of automatically.